By PIETY is to be understood wholehearted attachment to God, the sense of the hereafter, absolute sincerity, and thus a characteristic found quite generally in saints and a fortiori in messengers of Heaven; we mention it because in the life of the Prophet it appears with a particularly salient function, and because it prefigures in a sense the spiritual climate of Islam . . . On the plane of PIETY, attention must be drawn to the love of poverty, fasting and vigils . . . It should be added that by PIETY we must understand the state of spiritual servitude (‘ubudiyah) in the highest sense of the term, comprising perfect “poverty” (faqr, whence the word faqir) and “extinction” (fana’) before God, and this is not unrelated to the epithet “unlettered” (ummi) which is applied to the Prophet. Piety is what links us to God; in Islam this something is, first of all an understanding, as deep as possible, of the evident Divine Unity – for he who is “responsible” must grasp this evidentness and there is here no sharp demarcation between believing and knowing – and next it is a realization of the Unity beyond our provisional and unilateral understanding which is itself ignorance when regarded in the light of plenary knowledge: there is no saint (wali, “representative,” thus “participant”) who is not a “knower through God” (‘arif bi-Llah). This explains why in Islam PIETY, and a fortiori the sanctity which is its flowering, has an air of serenity; it is a PIETY whose essence opens into contemplation and gnosis. (GTUFS: UIslam, The Prophet)